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Late quaternary changes in Antarctic bottom water velocity inferred from sediment grain size in the northern Weddell Sea

Pudsey, Carol J.. 1992 Late quaternary changes in Antarctic bottom water velocity inferred from sediment grain size in the northern Weddell Sea. Marine Geology, 107 (1-2). 9-33. https://doi.org/10.1016/0025-3227(92)90066-Q

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Abstract/Summary

Newly formed bottom water (θ ≤ −0.7°C) in the northern Weddell Sea flows E or NE at speeds up to 10–15 cm/s, with velocity decreasing towards the centre of the Weddell Gyre (preliminary results from long-term current meter moorings). Upper Quaternary sediments from this area contain a fine-grained terrigenous component (from the nepheloid layer) plus biogenic silica (mostly diatoms) with a small amount of ice-rafted debris. In cores from between 61° and 66°S and from 3300 m to 4700 m water-depth, the proportion of biogenic silica increases northwards (corresponding to increasing seasonal extent of open water vs sea-ice cover), and the proportion of silt and well-sorted fine sand in surface sediments increases with average current velocity. Downcore, diatom-rich and diatom-poor sediments alternate on a scale of 1–3 m, and intervals with more diatoms contain a higher proportion of silt to clay. Preliminary stratigraphy suggests the cyclicity in composition and texture is related to glacial-interglacial cyclicity. During warm periods (indirectly correlated with isotope stages 1, 3, 5 etc.) biogenic silica production takes place during several months of each year, and silt and fine sand are transported by bottom currents. During glacial periods with greater sea-ice cover than at present, biogenic productivity was suppressed and no silica was preserved in the sediments: in addition, a lower proportion of terrigenous silt implies that bottom currents were weaker. At sites with a present-day average velocity of 10 cm/s, a Last Glacial Maximum average velocity of 1 cm/s or less is inferred from grain-size measurements.

Item Type: Publication - Article
Digital Object Identifier (DOI): https://doi.org/10.1016/0025-3227(92)90066-Q
ISSN: 00253227
Date made live: 03 Jan 2018 12:05 +0 (UTC)
URI: http://nora.nerc.ac.uk/id/eprint/518860

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